My outdoor marijuana plants are about a week away from harvest, but I’ve just noticed that a few of the top flowers are dying. They are dry and discolored. After investigating further, I noticed a larva chomping away. It looked almost indistinguishable from the leaf itself. What can I do to save my remaining flowers?
I’ve got a caterpillar that’s started eating away at my female marijuana plants. It’s about 1 to 2 mm in length with an off-white color. It spends most of its time crawling on the top side of the leaves, sucking them dry gradually and turning the affected areas brown. There are also a few tiny black specks and some honeydew contaminating the leaves. When my air-cooling system stopped working and the temperature increased from 70 to 78F to 80 to 92F, these pests increased. The humidity also rose another 20% because of the heat. Is there anything I can do?
Get rid of any caterpillars you come across, and check for more that you can just handpick. Once you’ve exhausted that avenue, try chemical or biological extermination agents.
Pyrethrum is an all-natural plant pesticide that comes from the concentrated secretions of a plant in the chrysanthemum family. Caterpillars and grubs are effectively killed by this pesticide. Just spray it onto the marijuana plant and watch as any remaining caterpillars stop eating and die. The pesticide won’t harm warm-blooded animals but it can be detrimental to cold-blooded animals like fish or reptiles. Thus, you shouldn’t use it around any cold-blooded pets or near any lakes or streams. Pyrethrum is useful for a limited time and comes in organic concoctions. Many marijuana growers use it for quick knockdowns. Read any instructions on a particular brand because some solutions are different than others. You can generally use most brands up until harvest time.
Another way to rid yourself of caterpillars is with bacillus thuringiensis (BT). It acts as an insect-specific plague that won’t harm anything but your grubs and caterpillars. In comes in many different brand names like Dipel. When sprayed on the plants, insects ingest it, get sick, stop eating, and die relatively quickly. When the insect dies, it releases more bacilli so that the infection is recurrent.
Botanigard is a fungus-based insecticide that is highly effective, but takes a couple days to really work its magic. You can use BT and Botanigard in conjunction with pyrethrum to cover all your bases.